Generally, the penetration of rain water or underground water into buildings or bridge decks reduces the bonding force of concrete material, causes pores and cracks due to the change in water volume caused by temperature change, and enlarges the cracks with the passage of time, resulting in a reduction in the strength and life span of structures forming the bridge decks.
Particularly in the case of bridge decks, as vehicles pass thereon, the deck slab thereof bends due to self-load and impact, and vibrations can occur, causing fine cracks in the pavement layer and thus separating the pavement layer from the bridge deck, such that rainwater or condensation water can infiltrate the deck slab to accelerate the cracking of the deck slab and corrode a structure or steel bars in the structure, causing the risk of a reduction in the life span and breakdown of the structure.
For this reason, a waterproofing material is required, and must have the capability to achieve the complete waterproofing of buildings and bridge decks and to absorb load and impact so as to inhibit the enlargement of cracks in the structure.
Meanwhile, for the complete waterproofing of buildings and bridge decks, various materials, including modified asphalt and rubber, are used. These materials must have various physical properties depending on the intended use thereof, and thus an improvement in the physical properties thereof is required in various fields.
For example, Japanese Patent Laid-Open Publication No. Sho 57-98559 discloses an asphalt which contains aromatic and/or naphthenic oil (or mineral oil) and thermoplastic rubber as additives for asphalt modification. The mineral oil has the effect of plasticizing the asphalt, and the thermoplastic rubber increases the softening point of the asphalt and makes the asphalt tough, but there is a problem in that a large amount of rubber is required in the asphalt in order to increase mechanical strengths, such as compression strength and tensile strength, and restoration ability to an original state thereof.
Japanese Patent Laid-Open Publication No. 57-139143 discloses a composition which contains a bitumiinous material (i.e., asphalt), a block copolymer (SBS, SIS or SEBS) of conjugated diene with vinyl aromatic hydrocarbon), a stabilizer containing nitrogen and sulfur atoms in the molecule, other various stabilizers, and a radical polymerization inhibitor.
Also, U.S. Pat. No. 4,485,201 discloses a method of producing an asphalt composition by preparing a blend of asphalt, ground rubber and a styrene-butadiene block copolymer and mixing the blend with a heat-resistant antioxidant, a tackifying agent, and process oil as a plasticizer or a softening agent, at a temperature of 149˜204° C.
According to the disclosure of said US patent, the composition exhibits good cohesion and adhesion at high temperatures, good flexibility at high and low temperatures, and excellent elasticity, and can be used as a crack sealer, a concrete joint sealer filler and an overlay sealant for construction materials.
However, this composition has a cone penetration of 60 and a flow of 20 mm at a softening point of 60° C. Thus, it has problems in that, when it is used as a waterproofing material for building roofs or as a crack-repairing material for road pavement in the summer season, it will undergo flow and plastic deformation, and when it is used as a road-repairing material, it will stain vehicle tires or the shoes of pedestrians.
Generally, in the summer season in Korea, the surface temperature of roads and roofs can increase to 60° C. or higher, but this temperature varies depending on the material and color of the surface. To overcome this shortcoming, organic fillers, including stone, aggregate, calcium carbonate, silica and talc, are frequently used, which increase the hardness, penetration value, softening point and the like, but decrease elongation and adhesive properties.
For example, a concrete pavement road sometimes consists only of concrete, but may also consist of an asphalt layer applied on a concrete layer in order to increase riding comfort and provide a waterproof effect. Particularly, in the case of bridges constructed with steel bars and concrete, the surface of the deck slab thereof is paved with asphalt, such that the deck slab surface is maintained in the same state as a road surface, and water is prevented from infiltrating into the concrete material.
In addition, in order to prevent the corrosion of both a concrete material, forming bridges, and steel bars, inserted into the concrete material, the infiltration of water is inhibited using various processes such as penetrating waterproofing, sheet waterproofing and membrane waterproofing. Nevertheless, water infiltrates the deck slab or pier of a bridge, thus reducing the life span of the bridge.
Due to the behavior of bridges or the traffic load applied to the bridge deck slab, the corrosion (cracking) of the bridge accelerates. In addition to this, due to the repeated freezing and thawing of water introduced into the corroded bridge, or due to the infiltration of chloride sprinkled to thaw the bridge deck slab, vertical or horizontal deformation and cracks in the deck slab (paved surface of the bridge) occur.
Korean Patent No. 0337443 discloses a composite waterproofing material for constructions such as buildings or bridges, which comprises a membrane material comprising 64% asphalt, 11% SBS thermoplastic rubber, 8% additive and 2˜8% filler, and a nonwoven fabric sheet having a molten coating material applied on the lower surface thereof such that the sheet is adhered to a membrane formed by the membrane material in order to protect the membrane. However, in said waterproofing material, there can be problems with respect to adhesion to the base of structures and a decrease in the adhesion thereof in response to temperature change. Also, it has low thermal resistance, resulting in damage to the waterproofing layer at high temperatures in the summer season.
Korean Patent No. 0377431 discloses a process of waterproofing the deck of a concrete bridge using a Guss material and a glassfiber mesh when paving the deck with asphalt. However, a waterproofing layer constructed using the process of said patent has problems with respect to crack bridging and low-temperature flexibility.
Korean Patent No. 0473730 discloses a method of waterproofing a concrete structure, comprising a first step of smoothing the surface of the concrete structure, a second step of coating an adhesive primer on the concrete structure surface, a third step of attaching a polymer resin-coated waterproof sheet onto the primer layer, and a fourth step of coating a urea polymer resin on the waterproof sheet, said waterproof sheet having a hardness of 40˜60 as measured by a Shore A-type hardness tester, and said urea polymer resin layer having a hardness of more than 90.
Korean Patent No. 0519459 discloses a material in which carbon fiber and glass fiber cross each other at a given interval in the form of a grid, and nonwoven fabric is attached to one surface of the grid consisting of carbon fiber and glass fiber, as well as a method for the reinforcement, waterproofing and snow-melting of a paved road using said material.
Korean Patent No. 0496627 discloses a composite waterproof layer formed by forming a sheet layer having a reinforced composite structure consisting of reinforced nowonven fabric, a thermoplastic synthetic polymer sheet, glass fiber and/or a film layer and then laminating a waterproof membrane layer on the nonwoven fabric bonded on the sheet layer, as well as a method for applying said reinforced composite layer using either an adhering method allowing partial insulation or an adhering method for additionally forming an adhered portion inside a corner.
However, the sheet layer for protecting the waterproofing material suggested in the prior art cannot ensure realization of a waterproofing material that is not broken by external force and has excellent physical properties.